Hi all,
I'm new designing PCB's and I have a problem with my board.
I used a CNC machine (**broken link removed**). The prototype is two layers where vias were connected with wire. All the components are SMT. I never used something like "ground plane" in the design. I just connected the circuit in Multisim and then transfer it to Ultiboard. Then routting connected pins and exporting to the CNC-362software. The machine do the job. Routes were 10milis wide and separation also 10milis.
The PCB includes an amplification analog stage (with opam's) and a digital processing stage. A PIC24f reads analog signals from the ADC, then it apply digital filters, and finally it sends the data to PC by USB link). The PC software plots in real time the read signals. The design also includes a switching regulator (MCP1727) reducing the 5V in the USB port to 3.3v required by the PIC24F. The PCB looks like a memory stick. Image attached.
Apparently everything works well on desktops. However, when I use a signal generator (TEK-AWG5000) to test the design on a laptop, the signal is a mess. Then, I used an oscilloscope (TEK-TDS1000B) to see the signal at the input pin on the microcontroller. Surprisingly, the signal becomes completely clean when I put the negative of the oscilloscope tip on the ground of my design (specifically, on the metal USB connector).
I read something in the web about ground plans and impedance couplers, which could be the solution to my problem.
I would appreciate any help you can give me.
Best regards
I'm new designing PCB's and I have a problem with my board.
I used a CNC machine (**broken link removed**). The prototype is two layers where vias were connected with wire. All the components are SMT. I never used something like "ground plane" in the design. I just connected the circuit in Multisim and then transfer it to Ultiboard. Then routting connected pins and exporting to the CNC-362software. The machine do the job. Routes were 10milis wide and separation also 10milis.
The PCB includes an amplification analog stage (with opam's) and a digital processing stage. A PIC24f reads analog signals from the ADC, then it apply digital filters, and finally it sends the data to PC by USB link). The PC software plots in real time the read signals. The design also includes a switching regulator (MCP1727) reducing the 5V in the USB port to 3.3v required by the PIC24F. The PCB looks like a memory stick. Image attached.
Apparently everything works well on desktops. However, when I use a signal generator (TEK-AWG5000) to test the design on a laptop, the signal is a mess. Then, I used an oscilloscope (TEK-TDS1000B) to see the signal at the input pin on the microcontroller. Surprisingly, the signal becomes completely clean when I put the negative of the oscilloscope tip on the ground of my design (specifically, on the metal USB connector).
I read something in the web about ground plans and impedance couplers, which could be the solution to my problem.
I would appreciate any help you can give me.
Best regards